I thought I had the same problem on my 190e. Bouncing the front left hard would get a bad squeek. Jacked up the car turned the steering wheel, horrible sqeak from the front left of car. Thought it was a strut, on a hunch changed the ball joint (much cheaper). When I took the old joint out, it was dry as a bone and full of dirt.
Squeek all gone now. Also eliminated a vibration I couldn't figure out.
My 2 cents!